The medical nanobots in my novel Small Miracles tap the energy sources that the patient’s own body provides. That is, they can metabolize glycerol and glucose, just as the cells in our bodies do.

Now what?

The good news is that being cell-sized, such bots can navigate the circulatory system, foraging for glucose as they go. But being cell-sized, we’ll also need a lot of such devices to accomplish anything useful in less than geological time. How will we control them all?

Maybe it’s best that we not control the nanobotsnot, anyway, in real time. Instead, maybe we’ll give each bot an onboard computer. Program the little guy to know what to do. As in, oversimplifying just a tad:

Drift through the bloodstream

Monitor your plaque sensors

When you find plaque on a blood-vessel wall

Grab hold

Nip the plaque into tiny pieces

Repeat

Such distributed control presupposes really tiny computers. And what about electricity to power them? To which I say: yes, and not necessary.

Yes, the computers must be really smalland they can be. And not necessary, because computers needn’t be electrical.

We’ve become accustomed to data storage in integrated circuits and on magnetic disks. But nothing says that a bit of dataa zero or a onemust be encoded as an electric quantity (like electrons trapped for a time in a charge well) or a magnetic quantity (like the polarization of a magnetic domain). Who remembers punch cards and paper tape? Really early computers used the presence or absence of pressure waves in a tank of mercury. And earlier still

Right. The abacus.

Anything that can unambiguously represent two valueswhile resisting, just a wee bit, randomly flipping from the state you want retained into the opposite statecan encode binary data. The position of sliding beads or rods. Or in an irreducible (I believe) minimum for any time soon, the state of individual bi-stable molecules. The medical nanobots in Small Miracles use bi-stable memory molecules.

That takes care of memory. What about a processing unit to execute instructions from, and manipulate data in, that memory? As it happens, the earliest digital computers were mechanical, designed by Charles Babbage). (Of course, so soon after Steampunk Month, everyone knows that. Right?)

Edward M. Lerner worked in high tech for thirty years, as everything from engineer to senior vice president. He writes near-future techno-thrillers, most recently Fools’ Experiments and Small Miracles, and far-future space epics like the Fleet of Worlds series with colleague Larry Niven. Ed blogs regularly at SF and Nonsense.